The Centers for Disease Control and Prevention says flatly, “Vaccines do not cause autism.” And “there is no link between vaccines and autism.” And “vaccine ingredients do not cause autism.”

Donald Trump sees it dangerously differently.

In March 2014, he tweeted: Healthy young child goes to doctor, gets pumped with massive shots of many vaccines, doesn’t feel good and changes — AUTISM. Many such cases!

In September 2014, he tweeted: I am being proven right about massive vaccinations—the doctors lied. Save our children & their future.

Worse, at a nationally televised presidential debate a year later, Trump drew ire and incredulity from the nation’s medical associations and patient advocacy groups saying there are “so many instances” of vaccinated children becoming autistic.

This week, Trump’s debunked views on vaccines were in the news again after Robert F. Kennedy Jr., an environmental attorney who also articulates discredited theories about vaccines and autism, met with Trump and told reporters he did so at the president-elect’s request “to make sure we have scientific integrity in the vaccine process for efficacy and safety of vaccines.” A day later, per Politico, Kennedy advised his environmental group that he will chair a vaccine safety commission for Trump. Trump’s team said no decision is made on Kennedy or the commission, but damage was done second-guessing such accepted science on so large a stage.

As The Washington Post columnist Charles Krauthammersays flatly, “Vaccination has prevented more childhood suffering and death than any other measure in history.”